A package called a Press Through Pack (PTP) is widely known as packaging for accommodating pharmaceuticals in the form of a plurality of tablets or capsules. A PTP, as will be described later in detail, is configured of a molded sheet formed of a thermoplastic synthetic resin having on one surface thereof a plurality of pocket-shaped molded portions, and a sealing sheet connected to the other surface of the molded sheet in such a manner that it closes off the openings of the pocket-shaped molded portions and protects a pharmaceutical accommodated within each of the pocket-shaped molded portions from the outer atmosphere.
A material such as a polyvinyl chloride resin, polypropylene resin, or polyethylene resin is used as the thermoplastic synthetic resin material that forms the molded sheet of this type of PTP, and aluminum foil coated with a heat-sealing agent or laminated with a heat-sealing film is typically used as the material of the sealing sheet.
In such a PTP, the water vapor and gas permeability of the molded sheet of a synthetic resin affects the stability of the object to be packaged, such as a pharmaceutical. Therefore, if a PTP is used to package an object that is readily affected by water vapor and gases, a layer of polyvinylidene chloride, which has an excellent barrier capability, is laminated over the molded sheet, in order to provide an even greater barrier effect.
Thus, a method of increasing the barrier capabilities of the molded sheet having pocket-shaped molded portions by laminating another layer over it has been proposed, but it is inevitably expensive and, in addition, unexpected problems have been cited as described below. The pocket-shaped molded portions of the molded sheet protrude out of one surface of that sheet and have a peripheral wall and a top wall, and the space therewithin opens outward into the other surface thereof, but the mold used during the molding processing stretches the material of a pocket-shaped molded portion of this type, which causes the top wall and also the peripheral edge between the top wall and the peripheral wall to thin. Since the pocket-shaped molded portions are inherently thinned locally by the molding processing, it is inevitable that there will remain some thinner portions in the top wall and peripheral edge after the molding operation, even if the barrier capabilities are increased by laminating a layer of polyvinylidene chloride thereover. Therefore, thickening the molded sheet by laminating it will not increase the barrier capability by much, but it will increase the cost and it will also increase the thickness of the molded sheet away from the pocket-shaped molded portions, where it is not necessary to have a barrier capability, while making it more difficult to push the packaged object out from within the pocket-shaped molded portions by a finger.
In addition, if the above polyvinylidene chloride layer with its high barrier capability is used as a partial laminate sheet, the inherently brittle polyvinylidene chloride will be unable to accommodate stretching of the material due to the molding processing, and fine cracks may occur. If cracking of this sort occurs, the barrier capabilities will deteriorate.
Further, although polyvinylidene chloride has excellent barrier capabilities, it is liable to discolor, so that, if the molded sheet is transparent, the discoloration can be seen from the outside in an unpleasant manner. In addition, when the molded sheet and the sealing sheet are heat-sealed together to form the package, there is a problem that bubbles are likely to occur.
It has been considered to apply the polyvinylidene chloride by coating instead of lamination, but, in this case too, problems similar to those described above occur. Further, it has been considered to use a fluorine-based resin as the laminate layer, but, in the same way as polyvinylidene chloride, a fluorocarbon resin cannot be said to be a good material from the viewpoint of protecting the Earth's environment and from recycling and incineration viewpoints. For example, although polyvinylidene chloride is considered to be preferable from the viewpoint of barrier capability, it emits chlorine when it is incinerated and thus it is particularly unfavorable from the viewpoint of environmental protection.
Alternatively, instead of increasing the protective capabilities of the molded sheet having pocket-shaped molded portions itself, a number of PTPs could be collected together and further packaged in a flexible packaging material containing aluminum foil. Packaging of this sort is usually called "pillow packaging" and PTPs that implement pillow packaging are further accommodated in boxes, and these have been put on the market. However, in this case, there are problems in that the packaged object cannot be seen, and also a much larger amount of packaging material is used overall, so the amount of useless waste increases and the dimensions of the outer box are also large. Packaging that uses pillow packaging takes up approximately 25% more space than packaging that doesn't use pillow packaging. The larger size of the overall package is a problem in that it makes it inconvenient from the point of view of transportation and storage.
The present invention was intended to solve the above described problems and has as its objective the provision of a novel type of packaging that is moisture-proof and has superior gas-barrier capabilities, and can moreover reduce the volume of packaging to make the above pillow packaging unnecessary, and also present few environmental pollution problems after disposal.
Another objective of the present invention is to provide a new method of manufacturing the above packaging.